System and method for measuring germanium concentration for manufacturing control of BiCMOS films

Abstract

A system and method is disclosed for measuring a germanium concentration in a semiconductor wafer for manufacturing control of BiCMOS films. Germanium is deposited over a silicon substrate layer to form a silicon germanium film. Then a rapid thermal oxidation (RTO) procedure is performed to create a layer of thermal oxide over the silicon germanium film. The thickness of the layer of thermal oxide is measured in real time using an interferometer, an ellipsometer, or a spectroscopic ellipsometer. The measured thickness of the layer of thermal oxide is correlated to a germanium concentration of the silicon germanium film using an approximately linear correlation. The correlation enables a value of the germanium concentration in the silicon germanium film to be provided in real time.

1. A method for manufacturing an integrated circuit device based on a germanium concentration of a silicon germanium film, said method comprising the steps of:
 performing a thermal oxidation procedure on said silicon germanium film to create a layer of thermal oxide over said silicon germanium film; 
 measuring a thickness of said layer of thermal oxide; 
 providing a correlation that relates a thickness of a layer of thermal oxide created over a silicon germanium film to a germanium concentration of said silicon germanium film; and 
 determining said germanium concentration of said silicon germanium film by identifying a value of germanium concentration that corresponds to said measured thickness of said layer of thermal oxide in accordance with said correlation; and 
 controlling manufacture of said integrated circuit device using said value of germanium concentration. 
 
   
   
     2. The method as set forth in  claim 1  wherein said step of measuring a thickness of said layer of thermal oxide comprises measuring said thickness of said layer of thermal oxide in real time using one of: an interferometer, an ellipsometer, and a spectroscopic ellipsometer. 
   
   
     3. The method as set forth in  claim 2  further comprising the step of:
 performing in real time said step of determining said germanium concentration of said silicon germanium film by identifying a germanium concentration that corresponds to said measured thickness of said layer of thermal oxide in accordance with said correlation. 
 
   
   
     4. The method as set forth in  claim 2  further comprising the step of:
 measuring said thickness of said layer of thermal oxide in real time by making a plurality of thickness measurements of said thickness of said layer of thermal oxide in real time using one of: an interferometer, an ellipsometer, and a spectroscopic ellipsometer. 
 
   
   
     5. The method as set forth in  claim 1  wherein said correlation that relates a thickness of a layer of thermal oxide created over a silicon germanium film to a germanium concentration of said silicon germanium film is an approximately linear correlation. 
   
   
     6. The method as set forth in  claim 5  wherein said approximately linear correlation is described by:
   Oxide Thickness (Å)=45.55035+2.2670656 Ge % 
 where said term Oxide Thickness is in units of Angstroms; and 
 where said term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     7. The method as set forth in  claim 5  wherein said approximately linear correlation is described by:
   Relative Oxidation Rate=0.9795774+0.0487541 Ge % 
 where said term Relative Oxidation Rate represents a ratio of a thickness of thermal oxide on a silicon germanium film to a thickness of thermal oxide on a silicon wafer without a silicon germanium film; and 
 where said term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     8. The method as set forth in  claim 5  wherein said approximately linear correlation is described by:
   Ge %=−20.03043+20.470103 Relative Oxidation Rate 
 where said term Relative Oxidation Rate represents a ratio of a thickness of thermal oxide on a silicon germanium film to a thickness of thermal oxide on a silicon wafer without a silicon germanium film; and 
 where said term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     9. A method for manufacturing an integrated circuit device based on a correlation between a germanium concentration of a silicon germanium film and a thickness of a layer of thermal oxide created over said silicon germanium film, said method comprising the steps of:
 creating a plurality of silicon germanium films in which each silicon germanium film has a different germanium concentration; 
 creating a layer of thermal oxide over each of said plurality of silicon germanium films; 
 measuring a thickness of each of said layers of thermal oxide; and 
 correlating said thickness of each of said layers of thermal oxide with a corresponding value of germanium concentration; and 
 controlling manufacture of said integrated circuit device using a value of germanium concentration obtained from said correlation. 
 
   
   
     10. The method as set forth in  claim 9  wherein said correlation between a germanium concentration of a silicon germanium film and a thickness of a layer of thermal oxide created over said silicon germanium film is an approximately linear correlation. 
   
   
     11. The method as set forth in  claim 10  wherein said approximately linear correlation is described by:
   Oxide Thickness (Å)=45.55035+2.2670656 Ge % 
 where the oxide thickness is in units of Angstroms and the term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     12. The method as set forth in  claim 10  wherein said approximately linear correlation is described by:
   Relative Oxidation Rate=0.9795774+0.0487541 Ge % 
 where said term Relative Oxidation Rate represents a ratio of a thickness of thermal oxide on a silicon germanium film to a thickness of thermal oxide on a silicon wafer without a silicon germanium film; and 
 where said term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     13. The method as set forth in  claim 10  wherein said approximately linear correlation is described by:
   Ge %=−20.03043+20.470103 Relative Oxidation Rate 
 where said term Relative Oxidation Rate represents a ratio of a thickness of thermal oxide on a silicon germanium film to a thickness of thermal oxide on a silicon wafer without a silicon germanium film; and 
 where said term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     14. A method for manufacturing an integrated circuit device based on a germanium concentration of a silicon germanium film, said method comprising the steps of:
 providing a silicon substrate layer; 
 depositing germanium on said silicon substrate layer to form a silicon germanium film; 
 performing a thermal oxidation procedure on said silicon germanium film to create a layer of thermal oxide over said silicon germanium film; 
 measuring a thickness of said layer of thermal oxide in real time; 
 providing a correlation that relates a thickness of a layer of thermal oxide created over a silicon germanium film to a germanium concentration of said silicon germanium film; 
 determining said germanium concentration of said silicon germanium film in real time by identifying a value of germanium concentration that corresponds to said measured thickness of said layer of thermal oxide in accordance with said correlation; and 
 controlling manufacture of said integrated circuit device using said value of germanium concentration. 
 
   
   
     15. The method as set forth in  claim 14  wherein said thermal oxidation procedure is one of: a rapid thermal oxidation procedure and a furnace oxidation procedure. 
   
   
     16. The method as set forth in  claim 14  wherein said step of measuring a thickness of said layer of thermal oxide in real time comprises measuring said thickness of said layer of thermal oxide within a time period of approximately five minutes using one of: an interferometer, an ellipsometer, and a spectroscopic ellipsometer. 
   
   
     17. The method as set forth in  claim 14  wherein said step of providing a correlation that relates a thickness of a layer of thermal oxide created over a silicon germanium film to a germanium concentration of said silicon germanium film comprises the step of:
 providing an approximately linear correlation described by:
   Oxide Thickness (Å)=45.55035+2.2670656 Ge % 
 
 where the oxide thickness is in units of Angstroms and the term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     18. The method as set forth in  claim 14  wherein said step of providing a correlation that relates a thickness of a layer of thermal oxide created over a silicon germanium film to a germanium concentration of said silicon germanium film comprises the step of:
 providing an approximately linear correlation described by:
   Relative Oxidation Rate=0.9795774+0.0487541 Ge % 
 
 where said term Relative Oxidation Rate represents a ratio of a thickness of thermal oxide on a silicon germanium film to a thickness of thermal oxide on a silicon wafer without a silicon germanium film; and 
 where said term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     19. The method as set forth in  claim 14  wherein said step of providing a correlation that relates a thickness of a layer of thermal oxide created over a silicon germanium film to a germanium concentration of said silicon germanium film comprises the step of:
 providing an approximately linear correlation described by:
   Ge %=−20.03043+20.470103 Relative Oxidation Rate 
 
 where said term Relative Oxidation Rate represents a ratio of a thickness of thermal oxide on a silicon germanium film to a thickness of thermal oxide on a silicon wafer without a silicon germanium film; and 
 where said term Ge % represents a germanium concentration in a silicon germanium film in terms of germanium percentage. 
 
   
   
     20. The method as set forth in  claim 14  wherein said step of depositing germanium on said silicon substrate layer to form a silicon germanium film comprises the step of:
 exposing said silicon substrate layer to a gas comprising silane gas and germane gas in a hydrogen gas carrier.